Double-sided slip-resistant material and method of making same

ABSTRACT

A double-sided, slip resistant material is produced using a blown film process which produces a film having an interior heat sealable layer, a core layer of flexible polyolefin and an exterior polyolefin elastomer layer in combination with a blowing agent and optionally grit to produce a double-sided slip resistant material. A number of rollers are provided after nip rollers have fused the film together, and which form part of a machine direction orienter (MDO) that is used in line in the manufacturing process to heat, and then cool and condition (anneal and relieve any stresses and/or thickness inconsistencies in the film) prior to the film being wound onto a roll for storage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/150,405 filed on Feb. 6, 2009 entitled “Double-SidedSlip-Resistant Material and Method of Making Same” which is incorporatedfully herein by reference.

TECHNICAL FIELD

The present invention relates to slip resistant material and moreparticularly, relates to a slip resistant, lightweight cloth-likematerial useful for products such as, but not limited to, a drop clothfor the moving and painting industry.

BACKGROUND INFORMATION

There is often a need for lightweight protective material such as dropcloths to cover floors and furniture during moving, construction orother activities such as painting and decorating. One problem that hasconsistently been struggled with for such material is the need of thematerial to be relatively impervious to liquids such as water and paint.

The prior art has dealt with the problem of waterproofing lightweightcloth materials by placing a plastic coating on one or both sides of apaper or cloth material. Unfortunately, although this makes the productwaterproof, it also makes it very slippery. If a painter cannot place aladder on the material without fear that it will slip out from under himor her, they are not apt to use it.

There have been some prior art attempts at making non-slip surfaces butthis relates mostly to roofing materials or more permanent material suchas floor tapes and the like.

Accordingly, what is needed is a lightweight, reusable, punctureresistant, cloth like material that is generally impervious to water andother liquids while providing at least one surface that is a non-slipsurface.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reading the following detailed description, takentogether with the drawings wherein:

FIG. 1 is a perspective schematic view of a portion of a system formaking the slip resistant material according to the present invention;and

FIG. 2 is a schematic diagram of the travel path of the double-sidedslip resistant material of the present invention after the material hasbeen blown showing incorporation of a machine direction orienter (MDO)in-line in the manufacturing process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention features a two-sided slip resistant material madeby the blown film process, which process is well known in the industry,comprising the co-extrusion of multiple layers to produce a finishedfilm composite having the desired characteristics described herein.

As illustrated in FIG. 1, a film blowing machine (not shown but wellknown in the art) produces a film “bubble” 10 comprising, in thepreferred embodiment and without limiting the present invention, 3layers or films: A, B and C. In the preferred embodiment, layer A, (theinside most layer of the bubble) is a heat sealable thermoplastic layerof approximately 0.2-2 mils in thickness having a softening point in therange of 110° to 200° F. which facilitates gluing of the two “A” layerstogether at a low temperature, as will be described below. Layer A maybe an EVA, EMA, LDPE or POP resin based layer. An advantage of using anEthyl Vinyl Acetate (EVA) layer is that the VA (vinyl acetate) contentmay be adjusted to achieve the desired softening point of the layer tofacilitate its gluing to an adjacent similar layer.

Layer B, the central or center layer, is preferably a flexiblepolyolefin layer having a thickness of approximately 0.5-2 mils.Suitable material for the center “B” layer include, LDPE, LLDPE, TPO,and POE. In addition to the resin this layer may also include acolorant, UV stabilizer, UV absorber and antioxidant, which will beexposed during the manufacturing process after the formation of thecollapsed bubbles in the C layer. An example of a potential UVStabilizer is Chimassorb 994™; examples of potential antioxidantsinclude Irganox 1010™, Irganox 1076™ and Irgafos 168™; and an example ofa potential UV Stabilizer is Cyasorb UV-531™.

The C layer (the outermost layer of the film which forms the top andbottom of the finished film product) is also a flexible polyolefinlayer. This layer, however, contains a “blowing” agent that causes thefilm to form many small “bubbles” on the exterior surface 12 of the Clayer. The blowing agent creates a gas in the extruder during themelting process and this gas is distributed throughout the “C” layer andis soluble in the molten plastic due to the high extruder pressure. Whenthe film exits the blown film die, there is a drop in pressure, andbubbles form in the “C” layer. By, stretching and cooling the film, thebubbles collapse forming a rough, nonslip open celled surface 12.

The blowing agent can be either a physical blowing agent (PBA) such ascarbon dioxide or butane, or an exothermic or endothermic chemicalblowing agent (CBA) such as a sodium bicarbonate and citric acidmixture, which decomposes under heat during the extrusion process andproduces a gas.

In the preferred embodiment, the preferred flexible polyolefin is apolyolefin elastomer (POE) such as Dow Chemical's “Engage” productpreferably, Engage grade 8003. After considerable experimentation, ithas been determined that not all polyolefin elastomers are suitable forthe skid resistance application. A resin with appropriate melting point,and softness to create bubbles that are very rubbery, flexible and havea high Coefficient of Friction (COF) creating a surface with significant“slip” resistance is required. These characteristics, which can be foundin the Engage 8003 product include: flexural modulus less than 200 MPa,and Durometer hardness (Shore A) less than 100.

In addition to the polyolefin elastomer, layer C may also include acoloring agent, to color the finished product, a UV stabilizer, UVabsorber and antioxidant, as well as a grit material such as ultra-highmolecular weight polyolefin which will adhere to the outside of thebubbles formed by the blowing agent and add additional slip resistanceto the finished film.

Near the top of the bubble 14, two rollers 16, 18 (top nip rollers) areutilized to “collapse” the bubble 14 causing both sides of the bubble tocome together. In the preferred embodiment, one of the rollers is arubber roller while the other is a metal nip roller, which is heated.The temperature of the nip is such that it is above the softening pointof the resin in the “A” layer. This causes the two inside “A” layers tofuse together forming a single film structure.

The processing of the fused film layer 20 is shown schematically in FIG.2. After the film 20 leaves the nip rollers 16/18, the film enters a setof in-line rollers 24-30, which serve as a Machine Direction Orienter(MDO) 22. The MDO rollers 22 serve as a post treatment of the film,annealing or conditioning the film to take any stresses out of the filmand to remove any variation in film thickness. The MDO section consistsof 2 sets of 2 rollers each. The first two rollers 24/26 are heated toabove the glass transition temperature of the resin of the inside Alayer of the film 20. These rollers operate at a speed, which is thesame as the speed at which the blown film 20 is manufactured.

The next two rollers 28/30 are cooling rollers operated at a temperaturein the range of 80-100° F. In addition, the cooling rollers 28/30 areoperated at a speed of 2% to 10% faster than the line or manufacturingspeed at which the first 2 rollers 24/26 operate, thus causing the nowfused, double-sided film to stretch in the region and directionindicated generally by arrow 32. The MDO section anneals the film, givesit a second heat treatment annealing the film and relieving it of anystresses.

The pair of cooling rollers 28/30 serve to cool the film down before itis wound into a roll for later use. Although the use of an MDO is knownin the art, it is not known to place such a device “in line” in themanufacturing process. Typically, in the prior art, a film is blown,wound onto a roll, subsequently unwound into an MDO for stretching, andthen rewound before use. Accordingly, the present invention provides adouble-sided non-slip, waterproof, plastic film which is easy andrelatively inexpensive to manufacture and which is very slip resistanton both sides, and can be used for numerous applications such aspainter's drop cloths, non-slip protective coverings, moving cloths andthe like.

Modifications and substitutions by one of ordinary skill in the art areconsidered to be within the scope of the present invention, which is notto be limited except by the allowed claims and their legal equivalents.

The invention claimed is:
 1. A method of making a double-sidedcloth-like film having a rough, slip-resistant, open-celled outersurface, said method comprising the following steps: using a filmblowing machine to coextrude a multilayer film from a circular die toform a tube having first and second sides, wherein the tube comprises atleast three coextruded layers of film including an inner layer, an outerlayer, and a middle layer, said inner layer comprising a thermoplasticheat sealable material having a predetermined softening point, whereinsaid outer layer comprises a plurality of gas bubbles resulting fromaddition of a blowing agent to its film making material provided to saidcircular die, said blowing agent causing said gas bubbles to form insaid outer layer as said outer layer is coextruded from the circulardie, and wherein each of said first and second sides of said tubeinclude said at least three layers; drawing the resulting coextrudedmultilayer film tube away from the circular die at a predeterminedspeed; at a predetermined distance from the circular die, collapsing thecoextruded multilayer film tube during said drawing by passing the filmtube between at least two rollers positioned in close proximity to oneanother so that a first roller of said at least two rollers contactssaid first side of the coextruded multilayer film tube and so that asecond roller of said at least two rollers contacts said second side ofsaid coextruded multilayer film tube, wherein said first roller is ametal nip roller heated to a temperature at or above the predeterminedsoftening point of said heat sealable inner layer, said temperaturesufficient to cause fusing of the inner layer of the first side with theinner layer of the second side, thereby causing the first and secondsides of the coextruded multilayer film tube to fuse into a double-sidedfilm, and wherein said second roller is a rubber roller; passing theresulting fused double-sided film through a pair of heated in-linerollers, wherein at least one of said pair of heated in-line rollers isheated to a temperature above the glass transition temperature of saidheat sealable inner layer, said pair of heated in-line rollers rotatingat approximately the same speed as said predetermined speed at which thecoextruded multilayer film tube is drawn from the circular die; andsubsequent to passing the fused double-sided film through said pair ofheated in-line rollers, passing the fused double-sided film through apair of cooled in-line rollers rotating faster than said pair of heatedin-line rollers to thereby cause the fused double-sided film to stretchin at least one direction, wherein at least one of said pair of cooledin-line rollers is operated at a temperature cooler than thepredetermined softening point of said heat sealable inner layer, andwherein said plurality of gas bubbles are collapsed by said stretchingand cooling, thereby forming said double-sided cloth-like film.
 2. Themethod of claim 1, wherein said inner layer comprises a materialselected from the group consisting of an EVA, EMA, LDPE or POP.
 3. Themethod of claim 1, wherein said inner layer comprises EVA having a vinylacetate content which is adjusted to achieve a desired predeterminedsoftening point.
 4. The method of claim 1, wherein said blowing agent isa physical blowing agent or an exothermic or endothermic chemicalblowing agent.
 5. The method of claim 4, wherein said physical blowingagent is selected from the group consisting of carbon dioxide andbutane.
 6. The method of claim 4, wherein said exothermic or endothermicchemical blowing agent comprises a combination of sodium bicarbonate andcitric acid.
 7. The method of claim 1, wherein said outer layercomprises at least one of the following: a coloring agent, UVstabilizer, a UV absorber, and an antioxidant.
 8. The method of claim 1,wherein the material of said outer layer is based on a polyolefinelastomer.
 9. The method of claim 1, wherein said outer layer furthercomprises a grit material which inheres to the outside of said gasbubbles formed by the blowing agent, thereby providing additional slipresistance to the outer surfaces of the cloth-like film.
 10. The methodof claim 1, wherein said middle layer comprises a polyolefin elastomer.11. A method of making a double-sided cloth-like film having a rough,slip-resistant, open-celled outer surface, said method comprising thefollowing steps: using a film blowing machine to coextrude a multilayerfilm from a circular die to form a tube having first and second sides,wherein the tube comprises at least three coextruded layers of filmincluding an inner layer, an outer layer, and a middle layer, said innerlayer comprising heat sealable EVA having a vinyl acetate content whichis adjusted to achieve a desired predetermined softening point, whereinsaid outer layer comprises a plurality of gas bubbles resulting fromaddition of a blowing agent to its film making material provided to saidcircular die, said blowing agent causing said gas bubbles to form insaid outer layer as said outer layer is coextruded from the circulardie, and wherein each of said first and second sides of said tubeinclude said at least three layers; drawing the resulting coextrudedmultilayer film tube away from the circular die at a predeterminedspeed; at a predetermined distance from the circular die, collapsing thecoextruded multilayer film tube during said drawing by passing the filmtube between at least two rollers positioned in close proximity to oneanother so that a first roller of said at least two rollers contactssaid first side of the coextruded multilayer film tube and so that asecond roller of said at least two rollers contacts said second side ofsaid coextruded multilayer film tube, wherein said first roller is ametal nip roller heated to a temperature at or above the predeterminedsoftening point of said heat sealable inner layer, said temperaturesufficient to cause fusing of the inner layer of the first side with theinner layer of the second side, thereby causing the first and secondsides of the coextruded multilayer film tube to fuse into a double-sidedfilm, and wherein said second roller is a rubber roller; passing theresulting fused double-sided film through a pair of heated in-linerollers, wherein at least one of said pair of heated in-line rollers isheated to a temperature above the glass transition temperature of saidheat sealable inner layer, said pair of heated in-line rollers rotatingat approximately the same speed as said predetermined speed at which thecoextruded multilayer film tube is drawn from the circular die; andsubsequent to passing the fused double-sided film through said pair ofheated in-line rollers, passing the fused double-sided film through apair of cooled in-line rollers rotating faster than said pair of heatedin-line rollers to thereby cause the fused double-sided film to stretchin at least one direction, wherein at least one of said pair of cooledin-line rollers is operated at a temperature cooler than thepredetermined softening point of said heat sealable inner layer, andwherein said plurality of gas bubbles are collapsed by said stretchingand cooling, thereby forming said double-sided cloth-like film.